docs: def _add(self, name, *args, **kw):
          """
          Add an argument to the underlying parser and grow the list
          .all_arguments and the set .names
          """
          argname = list(self.argdict)[self._argno]
          if argname != name:
              raise NameError(
                  'Setting argument %s, but it should be %s' % (name, argname))
          self._group.add_argument(*args, **kw)
          self.all_arguments.append((args, kw))
          self.names.append(name)
          self._argno += 1